Dextran sucrase catalyzes the formation of the polysaccharide, dextran, which is a significant component of dental plaque. The polymer is formed from sucrose, and therefore reaction is central to the interrelationship between the formation of dental caries from sugar. Work is proposed which will focus on the details of the reactions which the enzyme catalyzes. One reaction is the transfer of glucose residues to low molecular weight acceptors to form simple oligosaccharides. This reaction appears to compete with a second reaction, which is the rapid formation of a polymer. Previous studies have shown that the polymer is covalently attached to the enzyme. The mode of attachment is to be investigated, as well as the basis for the competition between the two reaction pathways. In addition studies will be carried out in order to determine whether the polymer, which is attached to the protein, will undergo hydrolysis or will be transferred as a group to an acceptor. The properties of the protein will also be examined. Earlier studies had indicated that it was a tetramer, and that the monomers were active. The characteristics of the monomers will be studied with regard to the reactions they catalyze, the amino acid composition and their relationship to the activity of the tetrameric protein.